if you are going to do less than 3 projects a month, start with what you have
If you are going to be running multiple projects, HD, or averaging 2 or more projects a month, then get an external
eSATA if you can hook it up to your computer
FW800 if your computer supports it
FW400 as last resort, but works fine for DV/HDV (less than 4 streams)
The Quad from G-Technology is pricey, but very flexible for you future needs and they make reliable eHDs. If you're going to get an external, do the math and find the sweet spot in the price points. Higher capacity, but not the highest one is usually about right.
iMovie '08 is pretty amazing if you're not already running FC.
I'm probably going to get flamed for this, but after having talked with and watched a presentation on iMovie '08 by it's creator, I believe it is a few generations ahead of Final Cut. It's missing a LOT of features and people are screaming for '07 back, but I believe it's the direction of future video editing.
My hearty recommendation to anyone that is not a professional or already heavily invested into Vegas, Avid, FC, to really spend the time in iMovie '08. I believe it fulfills 80%+ of what most people would be doing in the pricier programs.